No snake kills with more ruthless efficiency than the many-banded krait, which dwells in the jungles of India and Southeast Asia. Drop for drop, its venom is the deadliest of any land serpent’s, apart from a few rare species found only in the outback of Australia. One bite of the krait carries enough concentrated toxin to kill two dozen grown men.

American soldiers during the war in Vietnam called it the “two-step snake,” in the belief that its venom is so lethal that if it bites you, you will fall dead after taking just two steps. That’s an exaggeration, but the bite of the many-banded krait is astonishingly potent. The venom is a neurotoxin, which means that it disables the victim’s nervous system—like yanking an electrical plug out of the socket. Death comes when neurotransmission ceases: With no instructions to breathe, the muscles of the diaphragm are stilled, and the victim asphyxiates.

Usually the victim of the many-banded krait is another snake; because the species is cannibalistic, it might even be another krait. Yet it never seeks larger prey. The last thing it wants is a brush with a human being; the snake is far more likely to end up dead from the encounter than the person is. But the many-banded krait is built to kill, and if it is threatened, it can only do what it is programmed to do: It bites.

Most people go to great lengths to avoid meeting a many-banded krait, but in 2001, biologist Joe Slowinski traveled from San Francisco, where he was a curator of herpetology at the California Academy of Sciences, to Upper Burma, expressly to look for them—and all the other reptiles and amphibians he could find. Joe was one of the leading experts in the world on the venomous snakes of Asia, and his latest expedition was the most ambitious scientific mission in Burma’s history: He was leading fifteen naturalists and more than a hundred Burmese support staff into wilderness terrain that was scarcely known to science.

It might seem logical to deduce from the wide availability and superfine detail of satellite mapping that the wilderness of Earth has now been fully charted, all its secrets exposed. Yet that is far from the case: There are still vast tracts of the planet that remain almost unexplored. Burma, which many people now call Myanmar, the Southeast Asian country west of Thailand, is one of the most poorly studied places in the world. Neglected by British scientists in colonial times, ripped apart by civil war in the postwar period, and brutally plundered by its own corrupt military regime since a coup in 1988, Burma hasn’t had time for science. In his memoir Burma’s Icy Mountains, the British botanist Frank Kingdon-Ward, one of the few foreign explorers to venture there, observed after an expedition in 1937, “North Burma is an excellent example of a country which is surveyed but not explored.”

Since Kingdon-Ward’s day, much of the rest of the world has been studied intensively, but Burma remains terra virtually incognita—a potential treasure house for an enterprising biologist. When a former student of Joe Slowinski’s discovered a new species of nonvenomous snake in Louisiana a few months before Joe’s expedition, it was the first new serpent species to be identified in North America in more than half a century. Yet the wildlife of Burma remains so little known that Joe and his small band of American and Burmese colleagues discovered new species on virtually every expedition and projected that their research would eventually yield more than fifty previously unknown reptiles and amphibians—perhaps as many as one hundred and fifty. Here, in the foothills of the Himalayas, the most remote region he had yet studied, Joe expected to discover many new species.

Joe Slowinski and his team—botanists, ichthyologists, and ornithologists, experts on insects and mammals—were foot soldiers in Darwin’s army. Modern biologists, armed with sophisticated technology, are continuing the great intellectual adventure of compiling a comprehensive census of life on Earth, an audacious enterprise launched in the Enlightenment and given its theoretical foundation by Darwin himself, and carrying it forward into the twenty-first century.